转自:http://cai21cn.iteye.com/blog/700188

在开发一个web应用过程中,需要开发一个服务使用ftp功能将数据传输一个网外的ftp服务器。最初使用sun.net.ftp.ftpClient类,但是遇到问题,在网内测试没有问题,向网外传时报告失败。开发环境如下: 
web服务:tomcat 5.5.28 
OS平台:Linux 5 
java: 1.5 
失败报告:port命令失败,试试用pasv代替。代码如下:

  1. TelnetOutputStream os = null;
  2. FileInputStream in =null;
  3. try {
  4. logger.debug("开始上传文件"+sourceFile);
  5. java.io.File file_in = new java.io.File(sourceFile);
  6. in = new FileInputStream(file_in);
  7. //ftpClient.sendServer("TYPE I \r\n");
  8. //ftpClient.sendServer("PASV \r\n" );
  9. //logger.debug("发送TYPE I 和 PASC命令");
  10. // 命名文件,将文件名编码转为utf-8,否则中文文件名上载后为乱码文件名
  11. //os = ftpClient.put(new String(targetFile.getBytes("UTF-8")));
  12. os = ftpClient.put(targetFile);
  13. logger.debug("创建"+targetFile+" 成功");
  14. byte[] bytes = new byte[4096];
  15. int c;
  16. while ((c = in.read(bytes)) != -1) {
  17. os.write(bytes, 0, c);
  18. }
  19. } catch (IOException e) {
  20. logger.error(e.getMessage());
  21. return 0;
  22. } finally {
  23. if (in != null) {
  24. in.close();
  25. }
  26. if (os != null) {
  27. os.close();
  28. }
  29. }

代码在os = ftpClient.put(targetFile)这句出错,这样的代码在网上都很常见,但大约可以肯定的是许多的人只是拷贝复制下来构造一篇博文,并没有真正实践过。 
  试着给服务器发送PASV命令也不行。查看ftpClient的源代码,发现ftpClient在上载数据前首先尝试PASV模式,如PASV模式失败再使用PORT模式。通过TelnetOutputStream os = null此句代码,推测是否使用了telent功能,调整两边的路由器防火墙功能,折腾半死,程序失败依旧。 
  鉴于源代码使用telnetoutputStream,又没有控制传输模式的方法和命令,最后只好弃用sun.net.ftp.ftpClient,使用org.apache.commons.net.ftp.FTPClient类开发调试成功。部分代码如下:

  1. public boolean uploadFile(String fileName, String newName)
  2. throws IOException {
  3. boolean flag = false;
  4. InputStream iStream = null;
  5. try {
  6. iStream = new FileInputStream(fileName);
  7. ftpClient.enterLocalPassiveMode();
  8. logger.debug("Set pasv return code:"+ftpClient.getReplyCode());
  9. flag = ftpClient.storeFile(newName, iStream);
  10. logger.debug("upload file return code:"+ftpClient.getReplyCode());
  11. } catch (IOException e) {
  12. logger.debug("upload error:"+ftpClient.getReplyCode());
  13. flag = false;
  14. return flag;
  15. } finally {
  16. if (iStream != null) {
  17. iStream.close();
  18. }
  19. }
  20. return flag;
  21. }

  最后,找到java的老巢去,发现在java 1.5的文档里,有这样一段话:

Why Developers Should Not Write Programs 
That Call 'sun' Packages 
The classes that Sun includes with the Java 2 SDK, Standard Edition, fall into package groups java.*, javax.*, org.* and sun.*. All but the sun.* packages are a standard part of the Java platform and will be supported into the future. In general, packages such as sun.*, that are outside of the Java platform, can be different across OS platforms (Solaris, Windows, Linux, Macintosh, etc.) and can change at any time without notice with SDK versions (1.2, 1.2.1, 1.2.3, etc). Programs that contain direct calls to the sun.* packages are not 100% Pure Java. In other words:

The java.*, javax.* and org.* packages documented in the Java 2 Platform Standard Edition API Specification make up the official, supported, public interface. 
    If a Java program directly calls only API in these packages, it will operate on all Java-compatible platforms, regardless of the underlying OS platform.

The sun.* packages are not part of the supported, public interface. 
    A Java program that directly calls into sun.* packages is not guaranteed to work on all Java-compatible platforms. In fact, such a program is not guaranteed to work even in future versions on the same platform.

For these reasons, there is no documentation available for the sun.* classes. Platform-independence is one of the great advantages of developing in the Java programming language. Furthermore, Sun and our licensees of Java technology are committed to maintaining backward compatibility of the APIs for future versions of the Java platform. (Except for code that relies on serious bugs that we later fix.) This means that once your program is written, the class files will work in future releases. 
  具体URL:http://java.sun.com/products/jdk/faq/faq-sun-packages.html 
  真是为在sun.net.ftp上浪费掉的时间懊恼不已。 
  留文于此,希望广大朋友们在开发过程中少走弯路。 
  PS到处拷贝粘帖赚文章的“专业技术作家”!

---------------------------------

目前官方文章已经改写为:

Why Developers Should Not Write Programs  
That Call 'sun' Packages

The java.*, javax.* and org.* packages documented in the Java Platform Standard Edition API Specification make up the official, supported, public interface. 
If a Java program directly calls only API in these packages, it will operate on all Java-compatible platforms, regardless of the underlying OS platform.

The sun.* packages are  not part of the supported, public interface.  
A Java program that directly calls into sun.* packages is  not guaranteed to work on all Java-compatible platforms. In fact, such a program is not guaranteed to work even in future versions on the same platform.

Each company that implements the Java platform will do so in their own private way. The classes in sun.* are present in the JDK to support Oracle's implementation of the Java platform: the sun.* classes are what make the Java platform classes work "under the covers" for Oracle's JDK. These classes will not in general be present on another vendor's Java platform. If your Java program asks for a class "sun.package.Foo" by name, it may fail with ClassNotFoundError, and you will have lost a major advantage of developing in Java.

Technically, nothing prevents your program from calling into sun.* by name. From one release to another, these classes may be removed, or they may be moved from one package to another, and it's fairly likely that their interface (method names and signatures) will change. (From Oracle's point of view, since we are committed to maintaining the Java platform, we need to be able to change sun.* to refine and enhance the platform.) In this case, even if you are willing to run only on Oracle's implementation, you run the risk of a new version of the implementation breaking your program.

In general, writing java programs that rely on sun.* is risky: those classes are not portable, and are not supported.

 

开发FTP不要使用sun.net.ftp.ftpClient的更多相关文章

  1. 使用sun.net.ftp.FtpClient进行上传功能开发,在jdk1.7上不适用问题的解决

    问题如下图片: 之前项目上开发了一个上传文件的功能,使用的是sun.net.ftp.FtpClient这个类 连接服务器的代码大概如下: public static FtpClient ftpClie ...

  2. JAVA 实现FTP上传下载(sun.net.ftp.FtpClient)

    package com.why.ftp; import java.io.DataInputStream; import java.io.File; import java.io.FileInputSt ...

  3. python 开发一个支持多用户在线的FTP

    ### 作者介绍:* author:lzl### 博客地址:* http://www.cnblogs.com/lianzhilei/p/5813986.html### 功能实现 作业:开发一个支持多用 ...

  4. Python3学习之路~8.6 开发一个支持多用户在线的FTP程序-代码实现

    作业: 开发一个支持多用户在线的FTP程序 要求: 用户加密认证 允许同时多用户登录 每个用户有自己的家目录 ,且只能访问自己的家目录 对用户进行磁盘配额,每个用户的可用空间不同 允许用户在ftp s ...

  5. druapl-note1 本地开发上传模块不提示Ftp的警告

    刚安装完drupal之后,通过drupalxray 看到其它drupal网站安装的一些模块,下载好模块并安装时,提示需要输入Ftp信息. 但是本地开发不输入Ftp信息的(也不清楚自己的系统是否开启Ft ...

  6. FTP工具FileZilla&WinSCP与FTP类库FluentFTP

    FileZilla Filezilla分为client和server.其中FileZilla Server是Windows平台下一个小巧的第三方FTP服务器软件,系统资源也占用非常小,可以让你快速简单 ...

  7. java 上传文件到FTP(centos中的ftp服务)

    ftp服务器系统:centos7 提供ftp的服务:vsftpd pom.xml 依赖 <dependency> <groupId>commons-net</groupI ...

  8. 【转】Linux环境搭建FTP服务器与Python实现FTP客户端的交互介绍

    Linux环境搭建FTP服务器与Python实现FTP客户端的交互介绍 FTP 是File Transfer Protocol(文件传输协议)的英文简称,它基于传输层协议TCP建立,用于Interne ...

  9. linux上搭建ftp、vsftp, 解决访问ftp超时连接, 解决用户指定访问其根目录,解决ftp主动连接、被动连接的问题

    linux上搭建ftp 重要 解决如何搭建ftp         解决用户指定访问其根目录         解决访问ftp超时连接         解决ftp主动连接.被动连接的问题 1.安装ftp ...

随机推荐

  1. 【LeetCode】161. One Edit Distance

    Difficulty: Medium  More:[目录]LeetCode Java实现 Description Given two strings S and T, determine if the ...

  2. C语言中的地址传递(传指针,传递给形参的指针仍然是实参指针的一份拷贝)

    先看一个例子:这个程序为什么会崩溃? #include <stdio.h> #include <stdlib.h> int f(int *q) { ; q = (int*)ma ...

  3. ASP.net MVC把Html Table导出Excel

    [HttpPost] public ActionResult ExportExcel(FormCollection form) { string strHtml = form["hHtml& ...

  4. Avahi DOS攻击broadcast-avahi-dos

    Avahi DOS攻击broadcast-avahi-dos   Avahi是Linux下常用的类DNS服务.它可以帮助主机在没有DNS服务的局域网中,发现基于Zeroconf协议的设备和服务.该工具 ...

  5. AGC001 E - BBQ Hard 组合数学

    题目链接 AGC001 E - BBQ Hard 题解 考虑\(C(n+m,n)\)的组合意义 从\((0,0)\)走到\((n,m)\)的方案数 从\((x,y)\)走到\((x+n,y+m)\)的 ...

  6. BZOJ.1497.[NOI2006]最大获利(最小割 最大权闭合子图Dinic)

    题目链接 //裸最大权闭合子图... #include<cstdio> #include<cctype> #include<algorithm> #define g ...

  7. Python3练习题系列(09)——物以类聚,人以群分

    目标: 用类管理同类事物 解析: 用到“class”的编程语言被称作“Object Oriented Programming(面向对象编程)”语言.首先你需要做出“东西”来,然后你“告诉”这些东西去完 ...

  8. JavaScript_几种创建对象(2017-07-04)

    理解对象 1.创建Object实例 var clock = new Object(); clock.hour = 12; clock.minute = 10; clock.showHour = fun ...

  9. 【3dsmax2016】安装图文教程、破解注册以及切换语言方法

    第一步:安装3dsmax2014 64位中文版 第二步:解压3dsmax2014 64位中文版安装包 第三步:选择安装产品 第四步:接受相关协议 第五步:产品序列号和密钥 第六步:产品子组件选择 第七 ...

  10. mongodb副本集 statestr状态说明/解释

    STARTUP:刚加入到复制集中,配置还未加载 STARTUP2:配置已加载完,初始化状态 RECOVERING:正在恢复,不适用读 ARBITER: 仲裁者 DOWN:节点不可到达 UNKNOWN: ...